Semiconductor manufacturers have the cost saving goal of detecting and screening out defective integrated circuits as early as possible in the manufacturing process. In addition, the requirement of supplying "known good dice" to multi-chip module (MCM) manufacturers has increased the importance of this goal.
During a typical semiconductor manufacturing process, a plurality of integrated circuits are formed as individual dice on a semiconductor wafer. At present, each semiconductor wafer generally has dozens to hundreds of individual dice formed thereon. As integration geometries decrease and the size of semiconductor wafers increase, the number of integrated circuit dice formed on each wafer will most likely increase.
Once the dice are formed on a semiconductor wafer, the dice are then tested to determine which dice are functional and which dice are not functional. In most testing procedures, each die is probed using very costly probe equipment while the dice are still in wafer form. The presently available probe equipment is capable of only testing one or a few dice at a time. The presently available probe equipment contacts each bonding pad on an individual die with a separate probe needle.
While the dice are still in wafer form, each die is probed in order to determine whether each die passes a very basic opens/shorts test (e.g. a test for electrical opens or electrical shorts). In most cases, a full functional test is also performed using the probe equipment. However, no reliability testing is performed because it would be too costly to tie up the probe equipment testing one or a few dice at a time for the hours required for reliability testing.
The purpose of the wafer level probe test is to determine, as early as possible in the manufacturing process, whether each individual die is defective or not. The earlier a defective die is detected, the less money that is wasted on further processing of defective dice.
The dice are then separated or singulated into individual dice using any one of a variety of singulation techniques. In most cases, each die is then packaged in an integrated circuit package. Once the dice have been packaged, thorough electrical testing is performed on each of the packaged integrated circuits. The purpose of the thorough electrical testing is to determine whether each packaged integrated circuit properly performs the functionality specified by the semiconductor manufacturer. The tested, packaged integrated circuits are then sold.
In some cases, the packaged integrated circuits also undergo a reliability testing procedure called burn-in. Burn-in testing involves the testing of an integrated circuit for an extended period of time while the temperature of the integrated circuit is elevated above room temperature. In some cases, the heat generated by the integrated circuit itself is sufficient to elevate the temperature of the integrated circuit. In other cases, the temperature of the integrated circuit is raised by an apparatus external to the integrated circuit (e.g. a burn-in oven in which the packaged integrated circuits are placed).
Alternately, instead of or in addition to burn-in testing, cold temperature reliability testing may be performed. Cold temperature reliability testing involves the testing of an integrated circuit for an extended period of time while the temperature of the integrated circuit is decreased below room temperature.
Semiconductor manufacturers spend a significant amount of money packaging defective dice which pass the testing performed during probing, but which do not pass the reliability testing after packaging. In addition, the probe testing is redundant in that the same electrical tests are again performed on the individual integrated circuits after packaging.
The cost saving goal of detecting and screening out defective dice as early as possible in the manufacturing process is especially important in the context of multi-chip modules (MCMs). Multi-chip modules (MCMs) are electronic modules that include a plurality of integrated circuit dice which are packaged together as one unit. Multi-chip modules are becoming more widely used.
For multi-chip modules, it is quite costly to replace one or more failed dice once the dice have been bonded onto a substrate. Therefore, it is desirable to determine whether or not a die is fully functional and is reliable before the die is packaged as part of a multi-chip module. In addition, many manufacturers of multi-chip modules are requiring that semiconductor manufacturers sell them fully tested "known good dice" which have passed reliability tests and which are not packaged in an integrated circuit package.